[show scheduler] improve fallback from live dj to scheduled show

[mcfiredrill]

It may be possible to improve this so that the live dj won't cut off the start of the scheduled show if they go over their time.

on fallback from live to scheduled show

def on_track_change(s) =                                                                                                           
  # skip the playlist back to the beginning?                                                                                       
  source.skip(scheduled_shows)                                                                                                     
end                                                                                                                                
!live_dj = on_track(on_track_change, !live_dj)                                                                                     

[mcfiredrill]

Trying to think of how to get this to work, maybe we could hit the streampusher API inside of on_track_change, to reset the current song queue and queue up the scheduled show's entire playlist?